The purpose of the proposed research project is four-fold: 1) To quantitate by radioimmunoassay hormonal content (GH, TSH, ACTH, FSH, LH, and LTH) of the human fetal pituitary gland and hypothalamus from early gestation until 24 weeks and correlate this with age and sex, 2) To evaluate the hormonal releasing and/or synthesizing properties of various synthetic hypothalamic hormones, 3) To study the dynamics of pituitary hormonal secretion in vitro, 4) To study maternal-fetal endocrine relationships. The goals set for this year have been well realized. The major goal was the development of a radioimmunoassay for the hypothalamic hormone, LRF. With this very specific and sensitive assay we have been able to measure human fetal hypothalamic content of this hormone. With the development of this assay system we have shown that the hypothalami of saline aborted fetuses do contain LRF. This hormone has been found to be present in the youngest fetus (10 weeks) we have examined. In addition, the content of LRF in female hypothalami is greater than in male hypothalami and total content of LRF does increase with age of the fetus. We are presently in the process of correlating human fetal hypothalamic content of LRF with pituitary content of LH and FSH.